Search results for: tensile testing of damaged tows

Authors: Y. C. Ching, K. H. Chong

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The increasing of environmental awareness has led to grow interest in the expansion of materials with eco-friendly attributes. In this study, a 3 ply sandwich layer of kenaf fiber reinforced unsaturated polyester with various fiber orientations was developed. The effect of the fiber orientation on mechanical and thermal stability properties of polyester was studied. Unsaturated polyester as a face sheets and kenaf fibers as a core was fabricated with combination of hand lay-up process and cold compression method. Tested result parameters like tensile, flexural, impact strength, melting point, and crystallization point were compared and recorded based on different fiber orientation. The failure mechanism and property changes associated with directional change of fiber to polyester composite were discussed.

Keywords: kenaf fiber, polyester, tensile, thermal stability

Procedia PDF Downloads 354

Authors: Mehmet Ekici

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In this study, the fading time affecting the mechanical properties and microstructures of vermicular cast iron were studied. Pig iron and steel scrap weighing about 12 kg were charged into the high-frequency induction furnace crucible and completely melted for production of vermicular cast iron. The slag was skimmed using a common flux. After fading time was set at 1. 3 and 5 minutes. In this way, three vermicular cast iron was produced that same composition but different phase structures. The microstructure of specimens was investigated, and uni-axial tensile test and the Charpy impact test were performed, and their micro-hardness measurements were done in order to characterize the mechanical behaviours of vermicular cast iron.

Keywords: vermicular cast iron, fading time, hardness, tensile test and impact test

Procedia PDF Downloads 340

Authors: Aritra Majumdar

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While organizations strive to expand their new customer base, retaining existing relationships is a key aspect of improving overall profitability and also showcasing how successful an organization is in holding on to its customers. It is an experimentally proven fact that the lion’s share of profit always comes from existing customers. Hence seamless management of renewal journeys across different channels goes a long way in improving trust in the brand. From a quality assurance standpoint, time travel testing provides an approach to both business and technology teams to enhance the customer experience when they look to extend their partnership with the organization for a defined phase of time. This whitepaper will focus on key pillars of time travel testing: time travel planning, time travel data preparation, and enterprise automation. Along with that, it will call out some of the best practices and common accelerator implementation ideas which are generic across verticals like healthcare, insurance, etc. In this abstract document, a high-level snapshot of these pillars will be provided. Time Travel Planning: The first step of setting up a time travel testing roadmap is appropriate planning. Planning will include identifying the impacted systems that need to be time traveled backward or forward depending on the business requirement, aligning time travel with other releases, frequency of time travel testing, preparedness for handling renewal issues in production after time travel testing is done and most importantly planning for test automation testing during time travel testing. Time Travel Data Preparation: One of the most complex areas in time travel testing is test data coverage. Aligning test data to cover required customer segments and narrowing it down to multiple offer sequencing based on defined parameters are keys for successful time travel testing. Another aspect is the availability of sufficient data for similar combinations to support activities like defect retesting, regression testing, post-production testing (if required), etc. This section will talk about the necessary steps for suitable data coverage and sufficient data availability from a time travel testing perspective. Enterprise Automation: Time travel testing is never restricted to a single application. The workflow needs to be validated in the downstream applications to ensure consistency across the board. Along with that, the correctness of offers across different digital channels needs to be checked in order to ensure a smooth customer experience. This section will talk about the focus areas of enterprise automation and how automation testing can be leveraged to improve the overall quality without compromising on the project schedule. Along with the above-mentioned items, the white paper will elaborate on the best practices that need to be followed during time travel testing and some ideas pertaining to accelerator implementation. To sum it up, this paper will be written based on the real-time experience author had on time travel testing. While actual customer names and program-related details will not be disclosed, the paper will highlight the key learnings which will help other teams to implement time travel testing successfully.

Keywords: time travel planning, time travel data preparation, enterprise automation, best practices, accelerator implementation ideas

Procedia PDF Downloads 152

Authors: Dosu Malomo, O. E. Edeh, P. O. Okolo, F. C. Ibeh

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The preparation of various samples of ebonite vulcanizates and their physico-mechanical properties have been investigated using standard methods. This work explores the production of ebonite dust, production of ebonite vulcanizates and investigation of the characterisation of the ebonite. Five different ebonite materials – labelled A, B, C, D, and E with sulphur content in parts per hundred grams of rubber (Phr) of 32, 34, 36, 38 and 40 respectively were produced. The physico-mechanical properties carried out were tensile strength, hardness and abrasion resistance. The tensile strength (MPa) for sample A, B, C, D and E were 5.6, 3.5, 4.7, 1.7 and 2.0 respectively while the abrasion(%mass loss) were 8.49, 4.24, 2.59, 1.08 and 1.05 respectively and the hardness (IRHD) being 63, 64, 65, 70 and 82. The results show that the preparation of ebonite from natural rubber as a base polymer is feasible considering the results of characterisation obtained.

Keywords: compounding, ebonite dust, natural rubber, vulcanization

Procedia PDF Downloads 156

Authors: S. E. Mohmad-Saberi, W. Song, N. Oliver, M. Adrian, T.C. Hsu, A. Darbyshire

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Biodegradable polyurethane (PU) has emerged as a potential material to promote repair and regeneration of damaged/diseased tissues in heart valve regeneration due to its excellent biomechanical profile. Understanding the effects of sterilization on their properties is vital since they are more sensitive and more critical of porous structures compared to bulk ones. In this study, the effects of low concentration of hydrogen peroxide (H₂O₂) solution sterilization has been investigated to determine whether the procedure would be efficient and non-destructive to porous three-dimensional (3D) elastomeric nanocomposite, polyhedral oligomeric silsesquioxane-terminated poly (ethylene-diethylene glycol succinate-sebacate) urea-urethane (POSS-EDSS-PU) scaffold. All the samples were tested for sterility following sterilization using phosphate buffer saline (PBS) as control and 5 % v/v H₂O₂ solution. The samples were incubated in tryptic soy broth for the cultivation of microorganisms under agitation at 37˚C for 72 hours. The effects of the 5 % v/v H₂O₂ solution sterilization were evaluated in terms of morphology, chemical and mechanical properties using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and tensile tester apparatus. Toxicity effects of the 5 % v/v H₂O₂ solution decontamination were studied by in vitro cytotoxicity test, where the cellular responses of human dermal fibroblast (HDF) were examined. A clear, uncontaminated broth using 5 % v/v H₂O₂ solution method indicated efficient sterilization after 3 days, while the non-sterilized control shows clouding broth indicated contamination. The morphology of 3D POSS-EDSS-PU scaffold appeared to have similar morphology after sterilization with 5 % v/v H₂O₂ solution regarding of pore size and surface. FTIR results show that the sterilized samples and non-sterilized control share the same spectra pattern, confirming no significant alterations over the surface chemistry. For the mechanical properties of the H₂O₂ solution-treated scaffolds, the tensile strain was not significantly decreased, however, become significantly stiffer after the sterilization. No cytotoxic effects were observed after the 5 % v/v H₂O₂ solution sterilization as confirmed by cell viability assessed by Alamar Blue assay. The results suggest that low concentration of 5 % v/v hydrogen peroxide solution can be used as an alternative method for sterilizing biodegradable 3D porous scaffold with micro/nano-architecture without structural deformation. This study provides the understanding of the sterilization effects on biomechanical profile and cell proliferation of 3D POSS-EDSS-PU scaffolds.

Keywords: biodegradable, hydrogen peroxide solution, POSS-EDSS-PU, sterilization

Procedia PDF Downloads 158

Authors: C. P. Providakis, G. M. Angeli, M. J. Favvata, N. A. Papadopoulos, C. E. Chalioris, C. G. Karayannis

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An effort for the detection of damages in the reinforcement bars of reinforced concrete members using PZTs is presented. The damage can be the result of excessive elongation of the steel bar due to steel yielding or due to local steel corrosion. In both cases the damage is simulated by considering reduced diameter of the rebar along the damaged part of its length. An integration approach based on both electromechanical admittance methodology and guided wave propagation technique is used to evaluate the artificial damage on the examined longitudinal steel bar. Two actuator PZTs and a sensor PZT are considered to be bonded on the examined steel bar. The admittance of the Sensor PZT is calculated using COMSOL 3.4a. Fast Furrier Transformation for a better evaluation of the results is employed. An effort for the quantification of the damage detection using the root mean square deviation (RMSD) between the healthy condition and damage state of the sensor PZT is attempted. The numerical value of the RSMD yields a level for the difference between the healthy and the damaged admittance computation indicating this way the presence of damage in the structure. Experimental measurements are also presented.

Keywords: concrete reinforcement, damage detection, electromechanical admittance, experimental measurements, finite element method, guided waves, PZT

Procedia PDF Downloads 247

Authors: C. P. Providakis, G. M. Angeli, M. J. Favvata, N. A. Papadopoulos, C. E. Chalioris, C. G. Karayannis

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An effort for the detection of damages in the reinforcement bars of reinforced concrete members using PZTs is presented. The damage can be the result of excessive elongation of the steel bar due to steel yielding or due to local steel corrosion. In both cases the damage is simulated by considering reduced diameter of the rebar along the damaged part of its length. An integration approach based on both electro-mechanical admittance methodology and guided wave propagation technique is used to evaluate the artificial damage on the examined longitudinal steel bar. Two actuator PZTs and a sensor PZT are considered to be bonded on the examined steel bar. The admittance of the Sensor PZT is calculated using COMSOL 3.4a. Fast Furrier Transformation for a better evaluation of the results is employed. An effort for the quantification of the damage detection using the root mean square deviation (RMSD) between the healthy condition and damage state of the sensor PZT is attempted. The numerical value of the RSMD yields a level for the difference between the healthy and the damaged admittance computation indicating this way the presence of damage in the structure. Experimental measurements are also presented.

Keywords: concrete reinforcement, damage detection, electromechanical admittance, experimental measurements, finite element method, guided waves, PZT

Procedia PDF Downloads 285

Authors: Sanjeev Das

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In the present investigation, magnesium strips were produced by twin roll casting (TRC) and melt conditioned twin roll casting (MC-TRC) processes. The microstructures showed uniform fine equiaxed grain morphology in the case of MC-TRC cast samples. In the case of TRC samples elongated grains with centerline segregation was observed. Further investigation showed both the process has different solidification mechanism. Tensile tests were performed at 250–400ºC for both TRC and MCTRC samples. At 250ºC, MC-TRC sample showed significant improvement in strength and ductility. However, at higher temperatures the tensile properties were almost comparable, despite of TRC samples having larger grains compared to MC-TRC samples. It was observed that homogenized MC-TRC samples were easily hot stamped compared to TRC samples.

Keywords: MC-TRC, magnesium alloy, solidification, nucleation

Procedia PDF Downloads 182

Authors: Sayor Ajfar Aaron, Ashif Newaz, Sajjat Hossain Abir, Mushfiqur Rahman

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This paper examines the transformative potential of quantum computing in the field of cybersecurity, with a focus on advanced penetration testing and forensics. It explores how quantum technologies can be leveraged to identify and exploit vulnerabilities more efficiently than traditional methods and how they can enhance the forensic analysis of cyber-attacks. Through theoretical analysis and practical simulations, this study highlights the enhanced capabilities of quantum algorithms in detecting and responding to sophisticated cyber threats, providing a pathway for developing more resilient cybersecurity infrastructures.

Keywords: cybersecurity, cyber forensics, penetration testing, quantum computing

Procedia PDF Downloads 47

Authors: Yahaya Taiwo, Adedayo M. Segun

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This study investigated the effect of postweld soaking temperature on mechanical properties of AISI 1018 steel plate welded in aqueous environment. Pairs of 90 x 70 x 12 mm, AISI 1018 steel plates were welded with weld zone beyond distance 10 mm from weld centerline immersed in a water jacket at 25°C. The welded specimens were tempered at temperature of 200, 300, 400, 500 and 600°C for 1.5 hours. Tensile, hardness and toughness tests at distances 15, 30, 45 and 60 mm from the weld centreline with micro structural evaluation were carried out. The results show that the aqueous environment as-weld sample exhibited higher hardness and tensile strength values of 45.3 HV and 448.12 N/mm2 respectively while the hardness and tensile strength of aqueous environment postweld heat treated samples were 44.9 HV and 378.98 N/mm2. This revealed 0.82% and 15.4% reduction in hardness and strength respectively. The metallographic tests showed that the postweld heat treated AISI 1018 steel micro structure contained tempered martensite with ferritic structure and precipitation of carbides. Postweld heat treatment produced materials of lower hardness and improved toughness.

Keywords: air weld samples, aqueous environment weld samples, soaking temperature, water jacket

Procedia PDF Downloads 331

Authors: Mehmet Ekici

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The objective of this research is to investigate the effect of pouring temperature on the microstructure of the cast iron. The pattern was designed with 300 mm of width, and the thickness variations are 1.25 mm and poured at five different temperatures; 1300, 1325, 1350, 1375 and 1400°C. Several cast irons, prepared with different chemical compositions and microstructures (three lamellar and three spheroidal structures) have been examined by extensive mechanical testing and optical microscopy. The fluidity of spheroidal and lamellar graphite in cast iron increases with the pouring temperature. The numbers of nodules were decreased by increasing pouring temperature for spheroidal structures. Whereas, the numbers of flakes of lamellar structures changed by both pouring temperature and chemical composition. In general, with increasing pouring temperature, the amount of pearlite in the internal structure of both lamellar and spheroidal graphite cast iron materials were increased.

Keywords: spheroidal graphite cast iron, lamellar graphite in cast iron, pouring temperature, tensile test and impact test

Procedia PDF Downloads 324

Authors: Juraj Beniak, Ľubomír Šooš, Peter Križan, Miloš Matúš

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Within Rapid Prototyping technologies are used many types of materials. Many of them are recyclable but there are still as plastic like, so practically they do not degrade in the landfill. Polylactic acid (PLA) is one of the special plastic materials which are biodegradable and also available for 3D printing within Fused Deposition Modelling (FDM) technology. The question is, if the mechanical properties of produced models are comparable to similar technical plastic materials which are usual for prototype production. Presented paper shows the experiments results for tensile strength measurements for specimens prepared with different 3D printer settings and model orientation. Paper contains also the comparison of tensile strength values with values measured on specimens produced by conventional technologies as injection moulding.

Keywords: 3D printing, biodegradable plastic, fused deposition modeling, PLA plastic, rapid prototyping

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Authors: Michael T. Lobmann, Camilla Wellstein, Stefan Zerbe

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Vegetation plays an important role for the stabilization of slopes against erosion processes, such as shallow erosion and landslides. Plant roots reinforce the soil, increase soil cohesion and often cross possible shear planes. Hence, plant roots reduce the risk of slope failure. Generally, shrub and tree roots penetrate deeper into the soil vertically, while roots of forbs and grasses are concentrated horizontally in the topsoil and organic layer. Therefore, shrubs and trees have a higher potential for stabilization of slopes with deep soil layers than forbs and grasses. Consequently, research mainly focused on the vertical root effects of shrubs and trees. Nevertheless, a better understanding of the stabilizing effects of grasses and forbs is needed for better evaluation of the stability of natural and artificial slopes with herbaceous vegetation. Despite the importance of vertical root effects, field observations indicate that horizontal root effects also play an important role for slope stabilization. Not only forbs and grasses, but also some shrubs and trees form tight horizontal networks of fine and coarse roots and rhizomes in the topsoil. These root networks increase soil cohesion and horizontal tensile strength. Available methods for physical measurements, such as shear-box tests, pullout tests and singular root tensile strength measurement can only provide a detailed picture of vertical effects of roots on slope stabilization. However, the assessment of horizontal root effects is largely limited to computer modeling. Here, a method for measurement of in-situ cumulative horizontal root tensile strength is presented. A traction machine was developed that allows fixation of rectangular grass sods (max. 30x60cm) on the short ends with a 30x30cm measurement zone in the middle. On two alpine grass slopes in South Tyrol (northern Italy), 30x60cm grass sods were cut out (max. depth 20cm). Grass sods were pulled apart measuring the horizontal tensile strength over 30cm width over the time. The horizontal tensile strength of the sods was measured and compared for different soil depths, hydrological conditions, and root physiological properties. The results improve our understanding of horizontal root effects on slope stabilization and can be used for improved evaluation of grass slope stability.

Keywords: grassland, horizontal root effect, landslide, mountain, pasture, shallow erosion

Procedia PDF Downloads 160

Authors: Ahmed A.D. Sarhan, Chong Feng Duan, Mum Wai Yip, M. Sayuti

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Rapid Prototyping (RP) technologies enable physical parts to be produced from various materials without depending on the conventional tooling. Fused Deposition Modeling (FDM) is one of the famous RP processes used at present. Tensile strength and compressive strength resistance will be identified for different sample structures and different layer orientations of ABS rapid prototype solid models. The samples will be fabricated by a FDM rapid prototyping machine in different layer orientations with variations in internal geometrical structure. The 0° orientation where layers were deposited along the length of the samples displayed superior strength and impact resistance over all the other orientations. The anisotropic properties were probably caused by weak interlayer bonding and interlayer porosity.

Keywords: building orientation, compression strength, rapid prototyping, tensile strength

Procedia PDF Downloads 691

Authors: K. A. Weidenmann, M. Grigo, B. Brylka, P. Elsner, T. Böhlke

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In order to reduce fuel consumption, the weight of automobiles has to be reduced. Fiber reinforced polymers offer the potential to reach this aim because of their high stiffness to weight ratio. Additionally, the use of fiber reinforced polymers in automotive applications has to allow for an economic large-scale production. In this regard, long fiber reinforced thermoplastics made by direct processing offer both mechanical performance and processability in injection moulding and compression moulding. The work presented in this contribution deals with long glass fiber reinforced polypropylene directly processed in compression moulding (D-LFT). For the use in automotive applications both the temperature and the time dependency of the materials properties have to be investigated to fulfill performance requirements during crash or the demands of service temperatures ranging from -40 °C to 80 °C. To consider both the influence of temperature and time, quasistatic tensile tests have been carried out at different temperatures. These tests have been complemented by high speed tensile tests at different strain rates. As expected, the increase in strain rate results in an increase of the elastic modulus which correlates to an increase of the stiffness with decreasing service temperature. The results are in good accordance with results determined by dynamic mechanical analysis within the range of 0.1 to 100 Hz. The experimental results from different testing methods were grouped and interpreted by using different time temperature shift approaches. In this regard, Williams-Landel-Ferry and Arrhenius approach based on kinetics have been used. As the theoretical shift factor follows an arctan function, an empirical approach was also taken into consideration. It could be shown that this approach describes best the time and temperature superposition for glass fiber reinforced polypropylene manufactured by D-LFT processing.

Keywords: composite, dynamic mechanical analysis, long fibre reinforced thermoplastics, mechanical properties, time temperature superposition

Procedia PDF Downloads 194

Authors: A. S. Haruna, M. U. Tambawal, A. A. Salawu

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The psychological impact of peer influence on its individual group members, can make them resist HIV/AIDS counselling and testing. This study investigated the correlate of peer influence and resistance to HIV/AIDS counselling and testing among students in tertiary institutions in Kano state, Nigeria. To achieve this, three null hypotheses were postulated and tested. Cross-Sectional Survey Design was employed in which 1512 sample was selected from a student population of 104,841.Simple Random Sampling was used in the selection. A self-developed 20-item scale called Peer Influence and Psychological Resistance Inventory (PIPRI) was used for data collection. Pearson Product Moment Correlation (PPMCC) via test-retest method was applied to estimate a reliability coefficient of 0.86 for the scale. Data obtained was analyzed using t-test and PPMCC at 0.05 level of confidence. Results reveal 26.3% (397) of the respondents being influenced by their peer group, while 39.8% showed resistance. Also, the t-tests and PPMCC statistics were greater than their respective critical values. This shows that there was a significant gender difference in peer influence and a difference between peer influence and resistance to HIV/AIDS counselling and testing. However, a positive relationship between peer influence and resistance to HIV/AIDS counselling and testing was shown. A major recommendation offered suggests the use of reinforcement and social support for positive attitudes and maintenance of safe behaviour among students who patronize HIV/AIDS counselling.

Keywords: peer group influence, HIV/AIDS counselling and testing, psychological resistance, students

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Authors: Mohammed Alrefaie, Yaser Miaji

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Greenhouses provide a convenient means to grow plants in the best environment. They achieve this by trapping heat from the sunlight and using artificial means to enhance the environment of the greenhouse. This includes controlling factors such as air flow, light intensity and amount of water among others that can have a big impact on plant growth. The aim of the greenhouse is to give maximum yield from plants possible. This report details the development and testing of greenhouse environment control system that can regulate light intensity, airflow and power supply inside the greenhouse. The details of the module development to control these three factors along with results of testing are presented.

Keywords: greenhouse, control system, light intensity, comprehensive environment

Procedia PDF Downloads 474

Authors: C. Tezara, H. Y. Lim, M. H. Yazdi, J. W. Lim, J. P. Siregar

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Natural fibre has become an element in human lives. A lot of researchers have conducted research about natural fibre reinforced polymer. Malaysian government has spent a lot of money on the research funding for researchers and academician especially research on kenaf fibre due to exclusion of tobacco from AFTA (Asean Free Trade Area) list. This work is to investigate the mechanical properties of kenaf fiber reinforced epoxy composite where short kenaf fibre was applied and the mechanical properties of 5%, 10% and 15% wt. of kenaf fibre were added into the mixture of epoxy resin. Hand lay-up process was selected in the fabrication of the specimen for testing. The tensile, flexural and impact test were conducted following ASTM D3039, ASTM D790 and ASTM D256 accordingly. From the experiment result, the effect of different fiber loading of the specimen on its mechanical properties would be analyzed and compared in the result and discussion.

Keywords: Kenaf fibre, epoxy, composite, fibre

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Authors: Mustafa Kaya

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After the 1999 Marmara earthquake in Turkey research by the Turkish Precast Union stated that 24.50% of the precast structures were damaged with some of this damage being observed in the beam to column connections of the structures. Since it is essential to provide those rendered homeless by the earthquake with safe, habitable accommodation repairing medium and slight levels of damage at the connection parts should be undertaken. In order to prove that a repaired connection was sufficiently strong, a precast beam to column post tensioned connection was tested in three phases. In phase one, the middle level damage was observed at 6% drift at these connections. As a result of the extra loads applied, little damage was observed. In the last phase, the four connections tested in the first phase were repaired using epoxy resin and then retested. The results from the tests on the repaired precast and the undamaged specimens showed that the repaired specimens were sufficiently strong, thus proving that repair to damaged precast beam to column post tensioned connections can be undertaken.

Keywords: precast beam to column connection, moment-resisting connection, post-tensioned connections, repair of precast connections

Procedia PDF Downloads 438

Authors: Luvuno N. Jele, Warwick W. Hastie, Andrew Green

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Calcarenite is a clastic sedimentary beach rock composed of more than 50% sand sized (0.0625 – 2 mm) carbonate grains. In South Africa, these rocks occur as a narrow belt along most of the coast of KwaZulu-Natal and sporadically along the coast of the Eastern Cape. Calcarenites contain a high percentage of calcium carbonate, and due to a number of its physical and structural features, like porosity, cementing material, sedimentary structures, grain shape, and grain size; they are more prone to chemical and mechanical weathering. The objective of the research is to study the strength and compressibility characteristics of the calcarenites along the coast of KwaZulu-Natal to be able to better understand the geotechnical behaviour of these rocks, which may help to predict areas along the coast which may be potentially susceptible to failure/differential settling resulting in damage to property. A total of 148 cores were prepared and analyzed. Cores were analyzed perpendicular and parallel to bedding. Tests were carried out in accordance with the relevant codes and recommendations of the International Society for Rock Mechanics, American Standard Testing Methods, and Committee of Land and Transport Standard Specifications for Road and Bridge Works for State Road Authorities. Test carried out included: x-ray diffraction, petrography, shape preferred orientation (SPO), 3-D Tomography, rock porosity, rock permeability, ethylene glycol, slake durability, rock water absorption, Duncan swelling index, triaxial compressive strength, Brazilian tensile strength and uniaxial compression test with elastic modulus. The beach-rocks have a uniaxial compressive strength (UCS) ranging from 17,84Mpa to 287,35Mpa and exhibit three types of failure; (1) single sliding shear failure, (2) complete cone development, and (3) splitting failure. Brazilian tensile strength of the rocks ranges from 2.56 Mpa to 12,40 Ma, with those tested perpendicular to bedding showing lower tensile strength. Triaxial compressive tests indicate calcarenites have strength ranging from 86,10 Mpa to 371,85 Mpa. Common failure mode in the triaxial test is a single sliding shear failure. Porosity of the rocks varies from 1.25 % to 26.52 %. Rock tests indicate that the direction of loading, whether it be parallel to bedding or perpendicular to bedding, plays no significantrole in the strength and durability of the calcarenites. Porosity, cement type, and grain texture play major roles.UCS results indicate that saturated cores are weaker in strength compared to dry samples. Thus, water or moisture content plays a significant role in the strength and durability of the beach-rock. Loosely packed, highly porous and low magnesian-calcite bearing calcarenites show a decrease in strength compared to the densely packed, low porosity and high magnesian-calcite bearing calcarenites.

Keywords: beach-rock, calcarenite, cement, compressive, failure, porosity, strength, tensile, grains

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Authors: Afsaneh Jasmine Majidi

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Language testing is an important part of language teaching experience and language learning process as it presents assessment strategies for teachers to evaluate the efficiency of teaching and for learners to examine their outcomes. However, language testing is demanding and challenging because it should provide the opportunity for proper and objective decision. In addition to all the efforts test designers put to design valid and reliable tests, there are some other determining factors which are even more complex and complicated. These factors affect the educational system, individuals, and society, and the impact of the tests vary according to the scope of the test. Seemingly, the impact of a simple classroom assessment is not the same as that of high stake tests such as International English Language Testing System (IELTS). As the importance of the test increases, it affects wider domain. Accordingly, the impacts of high stake tests are reflected not only in teaching, learning strategies but also in society. Testing experts use the term ‘washback’ or ‘impact’ to define the different effects of a test on teaching, learning, and community. This paper first looks at the theoretical background of ‘washback’ and ‘impact’ in language testing by reviewing of relevant literature in the field and then investigates washback effects of IELTS test of on Iranian IELTS teachers and students. The study found significant relationship between the washback effect of IELTS test and teaching strategies of Iranian IELTS teachers as well as performance of Iranian IELTS candidates and their community.

Keywords: high stake tests, IELTS, Iranian Candidates, language testing, test impact, washback

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Authors: Rebeca Ramirez Acosta, Sebastian Lenhoff

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Decision makers worldwide need to determine if the implementation of a new market mechanism will contribute to the sustainability and resilience of the power system. Due to smart grid technologies, new products in the distribution and transmission system can be traded; however, the impact of changing a market rule will differ between several regions. To test systematically those impacts, a market categorization has been compiled and organized in a smart grid market testing toolbox. This toolbox maps all actual energy products and sets the basis for running a co-simulation test with the new rule to be implemented. It will help to measure the impact of the new rule, based on the sustainable and resilience indicators.

Keywords: co-simulation, electricity market, smart grid market, market testing

Procedia PDF Downloads 179

Authors: Gaoyang Meng, Philip Harrison

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When manufacturing composite laminates, the fibre directions within the laminate are never perfectly straight and inevitably contain some degree of stochastic in-plane waviness or ‘meandering’. In this work we aim to understand the relationship between the degree of meandering of the fibre paths, and the resulting uncertainty in the laminate’s final mechanical properties. To do this, a numerical tool is developed to automatically generate meandering fibre paths in each of the laminate's 8 plies (using Matlab) and after mapping this information into finite element simulations (using Abaqus), the statistical variability of the tensile mechanical properties of a [45°/90°/-45°/0°]s carbon/epoxy (IM7/8552) laminate is predicted. The stiffness, first ply failure strength and ultimate failure strength are obtained. Results are generated by inputting the degree of variability in the fibre paths and the laminate is then examined in all directions (from 0° to 359° in increments of 1°). The resulting predictions are output as flower (polar) plots for convenient analysis. The average fibre orientation of each ply in a given laminate is determined by the laminate layup code [45°/90°/-45°/0°]s. However, in each case, the plies contain increasingly large amounts of in-plane waviness (quantified by the standard deviation of the fibre direction in each ply across the laminate. Four different amounts of variability in the fibre direction are tested (2°, 4°, 6° and 8°). Results show that both the average tensile stiffness and the average tensile strength decrease, while the standard deviations increase, with an increasing degree of fibre meander. The variability in stiffness is found to be relatively insensitive to the rotation angle, but the variability in strength is sensitive. Specifically, the uncertainty in laminate strength is relatively low at orientations centred around multiples of 45° rotation angle, and relatively high between these rotation angles. To concisely represent all the information contained in the various polar plots, rotation-angle dependent Weibull distribution equations are fitted to the data. The resulting equations can be used to quickly estimate the size of the errors bars for the different mechanical properties, resulting from the amount of fibre directional variability contained within the laminate. A longer term goal is to use these equations to quickly introduce realistic variability at the component level.

Keywords: advanced composite laminates, FE simulation, in-plane waviness, tensile properties, uncertainty quantification

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Authors: Dong Xie, Jun Zhao, Yiming Weng

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One of the challenges in dental cement biomaterials is how to make a restorative with mechanical strengths and wear resistance that are comparable to contemporary dental resin composites. Currently none of the dental cement restoratives has been used in high stress-bearing sites due to their low mechanical strengths and poor wear-resistance. The objective of this study was to synthesize and characterize the poly(alkenoic acid)s with different molecular structures, use these polymers to formulate a dental cement restorative, and study the effect of molecular structures on reaction kinetics, viscosity, and mechanical strengths of the formed polymers and cement restoratives. In this study, poly(alkenoic acid)s with different molecular structures were synthesized. The purified polymers were formulated with commercial Fuji II LC glass fillers to form the experimental cement restoratives. The reaction kinetics was studied via 1HNMR spectroscopy. The formed restoratives were evaluated using compressive strength, diametral tensile strength, flexural strength, hardness and wear-resistance tests. Specimens were conditioned in distilled water at 37 oC for 24 h prior to testing. Fuji II LC restorative was used as control. The results show that the higher the arm number and initiator concentration, the faster the reaction was. It was also found that the higher the arm number and branching that the polymer had, the lower the viscosity of the polymer in water and the lower the mechanical strengths of the formed restorative. The experimental restoratives were 31-53% in compressive strength, 37-55% in compressive modulus, 80-126% in diametral tensile strength, 76-94% in flexural strength, 4-21% in fracture toughness and 53-96% in hardness higher than Fuji II LC. For wear test, the experimental restoratives were only 5.4-13% of abrasive and 6.4-12% of attritional wear depths of Fuji II LC in each wear cycle. The aging study also showed that all the experimental restoratives increased their strength continuously during 30 days, unlike Fuji II LC. It is concluded that polymer molecular structures have significant and positive impact on mechanical properties of dental cement restoratives.

Keywords: dental materials, polymers, strength, biomaterials

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Authors: Reza Behboodian

Abstract:

Monitoring the structural health and diagnosing their damage in the early stages has always been one of the topics of concern. Nowadays, research on structural damage detection methods based on vibration analysis is very extensive. Moreover, these methods can be used as methods of permanent and timely inspection of structures and prevent further damage to structures. Non-destructive methods are the low-cost and economical methods for determining the damage of structures. In this research, a non-destructive method for detecting and identifying the failure location in structures based on dynamic responses resulting from time history analysis is proposed. When the structure is damaged due to the reduction of stiffness, and due to the applied loads, the displacements in different parts of the structure were increased. In the proposed method, the damage position is determined based on the calculation of the strain energy difference in each member of the damaged structure and the healthy structure at any time. Defective members of the structure are indicated by the amount of strain energy relative to the healthy state. The results indicated that the proper accuracy and performance of the proposed method for identifying failure in structures.

Keywords: failure, time history analysis, dynamic response, strain energy

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Authors: Guneet Saini, Uthej Vattipalli

Abstract:

In a world with increased demand for sustainable construction, waste product of one industry could be a boon to the other in reducing the carbon footprint. Usage of industrial waste such as fly ash and ground granulated blast furnace slag have become the epicenter of curbing the use of cement, one of the major contributors of greenhouse gases. In this paper, empirical studies have been done to develop alkali activated self-compacting geopolymer concrete (GPC) using ground granulated blast furnace slag (GGBS), incorporated with 2% nano-silica by weight, through evaluation of its fresh and hardening properties. Experimental investigation on 6 mix designs of varying molarity of 10M, 12M and 16M of the alkaline solution and a binder content of 450 kg/m³ and 500 kg/m³ has been done and juxtaposed with GPC mix design composed of 16M alkaline solution concentration and 500 kg/m³ binder content without nano-silica. The sodium silicate to sodium hydroxide ratio (SS/SH), alkaline activator liquid to binder ratio (AAL/B) and water to binder ratio (W/B), which significantly affect the performance and mechanical properties of GPC, were fixed at 2.5, 0.45 and 0.4 respectively. To catalyze the early stage geopolymerisation, oven curing is done maintaining the temperature at 60˚C. This paper also elucidates the test results for fresh self-compacting concrete (SCC) done as per EFNARC guidelines. The mechanical properties tests conducted were: compressive strength test after 7 days, 28 days, 56 days and 90 days; flexure test; split tensile strength test after 28 days, 56 days and 90 days; X-ray diffraction test to analyze the mechanical performance and sorptivity test for testing of permeability. The study revealed that the sample of 16M concentration of alkaline solution with 500 Kg/m³ binder content containing 2% nano silica produced the highest compressive, flexural and split tensile strength of 81.33 MPa, 7.875 MPa, and 6.398 MPa respectively, at the end of 90 days.

Keywords: alkaline activator liquid, geopolymer concrete, ground granulated blast furnace slag, nano silica, self compacting

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Authors: Richard Ji

Abstract:

Nondestructive deflection testing has been accepted widely as a cost-effective tool for evaluating the structural condition of airfield pavements. Backcalculation of pavement layer moduli can be used to characterize the pavement existing condition in order to compute the load bearing capacity of pavement. This paper presents an improved best-fit backcalculation methodology based on deflection predictions obtained using finite element method (FEM). The best-fit approach is based on minimizing the squared error between falling weight deflectometer (FWD) measured deflections and FEM predicted deflections. Then, concrete elastic modulus and modulus of subgrade reaction were back-calculated using Heavy Weight Deflectometer (HWD) deflections collected at the National Airport Pavement Testing Facility (NAPTF) test site. It is an alternative and more versatile method in considering concrete slab geometry and HWD testing locations compared to methods currently available.

Keywords: nondestructive testing, pavement moduli backcalculation, finite element method, concrete pavements

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Authors: Ramezani M., Neitzert T.

Abstract:

This paper investigates mechanical properties and formability of the AZ61 magnesium alloy at high temperatures. Tensile tests were performed at elevated temperatures of up to 400ºC. The results showed that as temperature increases, yield strength and ultimate tensile strength decrease significantly, while the material experiences an increase in ductility (maximum elongation before break). A finite element model has been developed to further investigate the formability of the AZ61 alloy by deep drawing a square cup. Effects of different process parameters such as punch and die geometry, forming speed and temperature as well as blank-holder force on deep drawability of the AZ61 alloy were studied and optimum values for these parameters are achieved which can be used as a design guide for deep drawing of this alloy.

Keywords: AZ61, formability, magnesium, mechanical properties

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Authors: Jeon Chi-Ho, Lee Jae-Bin, Shim Chang-Su

Abstract:

National bridge inventory in Korea shows that the number of old prestressed concrete (PSC) bridgeover 30 years of service life is rapidly increasing. Recently tendon corrosion is one of the most critical issues in the maintenance of PSC bridges. In this paper, mechanical properties of corroded strands, which were removed from old bridges, were evaluated using tensile test. In the result, the equations to express the mechanical behavior of corroded strand were derived and compared to existing equation. For the decision of tendon replacement, it is necessary to evaluate the effect of corrosion level on strength and ductility of the structure. Considerations on analysis of PSC girders were introduced, and decision making on tendon replacement was also proposed.

Keywords: prestressed concrete bridge, tendon, corrosion, strength, ductility

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Authors: Sujit Kumar Pradhan, Anil Kumar, Vijay Kumar

Abstract:

The testing process of the software during the software development time is a crucial step as it makes the software more efficient and dependable. To estimate software’s reliability through the mean value function, many software reliability growth models (SRGMs) were developed under the assumption that operating and testing environments are the same. Practically, it is not true because when the software works in a natural field environment, the reliability of the software differs. This article discussed an SRGM comprising change-point and imperfect debugging in a simulated testing environment. Later on, we extended it in a multi-release direction. Initially, the software was released to the market with few features. According to the market’s demand, the software company upgraded the current version by adding new features as time passed. Therefore, we have proposed a generalized multi-release SRGM where change-point and imperfect debugging concepts have been addressed in a simulated testing environment. The failure-increasing rate concept has been adopted to determine the change point for each software release. Based on nine goodness-of-fit criteria, the proposed model is validated on two real datasets. The results demonstrate that the proposed model fits the datasets better. We have also discussed the optimal release time of the software through a cost model by assuming that the testing and debugging costs are time-dependent.

Keywords: software reliability growth models, non-homogeneous Poisson process, multi-release software, mean value function, change-point, environmental factors

Procedia PDF Downloads 67